The World Meteorological Organization (WMO) defines the atmosphere as an
hypotetical vertical distribution of atmospheric temperature, pressure and
density which by international agreement and for historical reasons, is roughly
representative of year-round, midlatitude conditions.

During the last years different astmospheric models have been developed. The
most complex ones take into account variables such us gravity decay with
distance or even solar flux on its minimum and maximum mean values along year.

Even it is possible to find atmospheric models not only for the Earth but also
for other Solar System planets such us Venus or Mars.

Following collection of models was directly taken from AIAA’s paper: Guide to
Reference and Standard Atmosphere Models which should be checked if more
information on the models is desired.